1. Field of the Invention
The present invention relates to moisture-curing, one-component coating compositions based on a polyisocyanate component containing a mixture of certain aromatic and aliphatic polyisocyanates and to the use of these coating compositions for the production of coatings.
2. Description of the Prior Art
Moisture-curing coating compositions containing organic polyisocyanates, more particularly NCO prepolymers of relatively high molecular weight, as binders are known (cf. for example H. Kittel, Lehrbuch der Lacke und Beschichtungen, 1973, Verlag W. A. Colomb.; Vol. 1, Part 2, pages 573 to 576 or Houben-Weyl, Methoden der organischen Chemie, Vol. E20, page 1646, Georg Thieme Verlag 1987). The curing reaction of the polyisocyanates with atmospheric moisture is inevitably accompanied by the formation of carbon dioxide which must escape from the coating. This results in a fundamental disadvantage of moisture-curing, one-component polyurethane lacquers, namely that lacquer systems such as these can only be applied in a maximum layer thickness of up to 300 .mu.m. If the lacquer systems are applied in greater layer thicknesses, the carbon dioxide is unable to escape from the coating, resulting in bubble formation. Accordingly, to obtain high layer thicknesses, a moisture-curing, one-component polyurethane coating has to be applied to the substrate in several operations which is attended in particular by economic disadvantages.
Accordingly, an object of the present invention is to provide binders for one-component coating compositions which may be cured without bubbles in high layer thicknesses.
This object may be achieved with the coating compositions according to the invention which are described in detail hereinafter.